Digestion apparatus and method



Feb. 6, 1962 A. FERRARI 3,020,130

DIGESTION APPARATUS AND METHOD Filed Aug. 6, 1959 '3 Sheets-Sheet 1 Tij- 1..

IN V EN TOR. 4/YD4PE.S FE$QAQI ATTOQNEY Feb. 6, 1962 A. FERRARI DIGESTION APPARATUS AND METHOD '3 Sheets-Sheet 2 Filed Aug. 6, 1959 IN VEN TOR. AIYDP'S Fae/9 4 21 BY M31 w A rrOIPNC Y Feb. 6, 1962 Filed Aug. 6, 1959 A. FERRARI DIGESTION APPARATUS AND METHOD '3 Sheets-Sheet 3 INVENTOR. Agypqas FEQQA 47/ 'm CELL ,4 rropn/EY United States Patent Ofiice 3,020,130 Patented Feb. 6, 1962 3,020,130 DIGESTION APPARATUS AND METHOD Andres Ferrari, Scarsdale, N.Y., assignor to Technicon Instruments Corporation, Chauncey, N.Y., a corporation of New York Filed Aug. 6, 1959, Ser. No. 832,002 19 Claims. (Cl. 23230) The present invention relates to a digestion method and apparatus which, while useful for other purposes, is intended primarily for performing Kjeldahl type of total or partial nitrogen determinations.

The conventional well known methods for total nitrogen determinations involve decomposition of nitrogen compounds with strong sulfuric acid or a mixture of sulfuric and phosphoric acids as a result of which the nitrogen bearing material is oxidized and ammonium sulfate is formed, and subsequent treatment with sodium hydroxide releases the ammonia nitrogen which can be measured by many colorimetric procedures. Subsequent to the digestion phase, the ammonia can be removed by distillation. Methods of the above indicated type are known as the Kjeldahl method and has been adapted for the determination of nitrogen in azines, hydrazones, oximes, semicarbazones, nitril compounds, azide nitrogen, etc.

Heretofore the Kjeldahl type of nitrogen determinations were performed on one sample at a time in a discontinuous or batch process and required, for each determination, complicated and expensive apparatus and procedures and the use of many articles of glassware and auxiliary apparatus.

The primary object of the present invention is to pro vide a method of nitrogen determination which may be performed continuously and successively on an indefinite number of samples by a continuous operation of the same apparatus without requiring frequent interruptions of the operation of the apparatus for cleaning or other purposes.

Briefly described, the method of the present invention involves digestion of the substances under investigation in a continuous digestion apparatus, dilution and treatment of the sample or substance under investigation with an alkali to release the ammonia, and treatment for colorimetric examination, specifically the addition of alkaline phenol and sodium hypochlorite to produce an intense blue color.

Another primary object of the invention is the provision of apparatus which may be operated continuously for performing the above described continuous method of the present invention.

The above and other objects, features and advantages of this invention will be fully understood from the following description considered in connection with the accompanying illustrative drawings.

In the drawings:

FIG. 1 is a more or less diagrammatic view illustrative of the method and apparatus of the present invention;

FIG. 2 is a side view of the continuously operated digestor, with parts broken away for the purpose of illustration;

FIG. 3 is an end view of the digestor;

FIG. 4 is a sectional view on the line 4-4 of FIG. 2; and

FIG. 5 is a longitudinal sectional view of the digestor cylinder, showing certain associated tubing in elevation.

Referring now to the drawings in detail and first to FIG. 1, the digestion apparatus of the present invention comprises a proportioning pump which is schematically illustrated and may be of any suitable type, although it is preferably of the type described in US. Patent No.

2,893,324 issued to the assignee of the present application.

Briefly described, as shown in said patent, the pump comprises a plurality of resiliently compressible tubes which are compressed progressively along their lengths, for the pumping operation, by the engagement therewith of a plurality of pressure rollers which move longitudinally of the pump tubes to fully close said tubes progressively along their lengths and thus propel the liquids or other fluids for transmitting them from sources of supply to points of delivery. As here shown, the sample to be digested is transmitted by the pump tube 12. The acid is transmitted by the pump tube 14 and air or other inert gas is transmitted by the pump tube 16 to a fitting 18 which is connected to a glass helical mixing coil 20 from which these fluids flow through a tube 22 to the inlet end of the liquid-heating or digestion cylinder 24 which is disposed within an electrically heated oven 26 (FIGS. 3 to 5). As hereinafter described in detail, digestion cylinder 24 is mounted for rotation in the housing of oven 26 and is provided with a helical groove 28 so that the liquid which is supplied to said cylinder through tube 22 is heated to a high temperature as it moves along the groove 28 from the inlet end of the cylinder to the outlet end thereof. The opposite ends of the helical groove 28 terminate at the inlet and outlet grooves 30 and 32, respectively, in communication therewith, said grooves 30 and 32 being at right angles to the axis of rotation of cylinder 24. An oiftake tube 34 has its inlet end 36 disposed in groove 32 for removing the concentrated and digested liquid from the cylinder 24 at a point spaced longitudinally of the cylinder downstream from the inlet groove 30, said offtake tube 34 being connected to one end of a glass helical cooling coil 38. A pump tube 40 is connected at the outlet end of cooling coil 38 for supplying water to the concentrated digested material for diluting said material, said pump tube 40 being for that purpose connected to the tube 42 which is connected to the cooling coil 38. Tube 42 is connected to the inlet end of pump tube 44 and the digested material is further diluted by the addition of water supplied by pump tube 46 which, together with tube 44, is connected to the fitting 48. The outlet end of fitting 48 is connected to the glass helical mixing coil 50 for thoroughly mixing the digested material in the water during the passage of the liquids through coil 50. The oulet end of mixing coil 50 is connected by a tube 52 to an overflow receptacle 54 which, as here shown, is in the form of a U-shaped tube having an inlet leg 56 and an outlet leg 58, both of which are open at their upper ends. An overflow tube 60 is connected to leg 58 for the passage of excess liquid from the overflow device. A tube 62 is in communication at its intake end 64 with leg 58 of the overflow supply receptacle for the supply of the diluted digested material to the pump tube 66 through which the material is pumped for treatment with an alkali, namely, sodium hydroxide supplied by the pump tube 68. Said pump tubes 66, 68 and an air supply pump tube 70 are connected to a fitting 72 which is connected to the helical glass mixing coilr74. In the course of the passage of the diluted digested material and the sodium hydroxide through the mixing coil 74, the sodium hydroxide neutralizes the acid content of the liquid containing the digested material and liberates ammonia (NH but the liberated ammonia gas (NH immediately goes into solution in the water forming ammonium hydroxide (NH OH) It will be understood that the quantity of NH is used as a measure of the nitrogen in the sample.

The outlet of the mixing coil 74 is connected by a tube 76 to the inlet of a helical glass mixing coil 78.

nected to the outlet of said mixing coil and then passes through the heating bath 86 which is maintained at a temperature of 95 C. From the heating bath 86 the liquid treated for colorimetric examination passes through a glass cooling coil 88 and from the latter through the flow cell of the colorimeter 90 for controlling the operation of the colorimeter recorder 92.

The treatment of the liquid with alkaline phenol and sodium hypochlorite for colorimetric examination is well known and as it does not per se form part of the present invention, further description thereof is unnecessary. It may be noted, however, that as a result of this treatment an intense blue color is obtained, the density of the color being proportional to the quantity of ammonia in the liquid and provides an indication of the quantity of nitrogen in the investigated sample.

Referring more particularly to FIGS. 1 and 5, it will be observed that an offtake tube 94 has its inner end in communication with digestor cylinder 24 at the inlet end thereof. The purpose of this is to remove gaseous fumes which result from the heating of the acid in cylinder 24. Said tube 94 is connected to an aspirator 96 of a well known type which is operated by means of a stream of water for withdrawing the fumes and for diluting the acid of which the fumes are constituted sufliciently to produce a sufficiently weak acid solution which may safely be transmitted through the outlet 98 of the aspirator for disposal in a waste pipe.

Also, as illustrated more clearly by FIGS. 1 and 5, the overflow tube 100 has its inlet end positioned in digestor cylinder 24 at the outlet end thereof for removing excess liquid which may accumulate in the outlet groove 32 of said cylinder. In this connection, it will be observed that the lower inlet end of tube 100 is above the lower inlet end of ofitake tube 34. Tube 100 is connected to the helical glass cooling coil 102 and water for diluting the liquid which passes through said cooling coil is supplied by the branch tube 104. A tube 106 is connected to the pump tube 108 for pumping the diluted excess liquid from tube 106 to waste.

The digestion apparatus will now be further described with more particular reference to FIGS. 2 to 5. Said apparatus comprises the above-mentioned housing which includes the lower insulated semi-cylindrical section 110 and the upper semi-cylindrical section 112 hinged to section 110 in any suitable way as by the hinge 114 so that section 112 can be moved to a retracted position (FIG. 3) to provide access to the interior of the housing. Both sections are provided with electric resistance heating elements 116 to provide sufiicient heat for the digestion process. It will be noted that as illustrated in FIG. a relatively small quantity of the liquid containing the sample to be digested is admitted into the inlet end of the cylinder 24 so that said liquid is heated to a high temperature during the course of the movement of the liquid in the helical groove 28 as a result of the rotation of the cylinder 24. Housing 26 is supported in stationary position by the frame members 120 on the base 122.

Cylinder 24 is mounted at its opposite ends by resilient washers 124 in driven rollers 126 whereby rotation of said rollers rotate said cylinder about its longitudinal axis. The driven rollers 126 at each end of the cylinder 24 are supported by a pair of laterally spaced rollers 128. Said rollers 128 are each provided with a peripheral groove 130 in which the marginal peripheral edge portion of the companion driven roller is engaged. It will be understood that the rollers 128 not only rotate the rollers 126 and thereby rotate cylinder 24, but also support said rollers in horizontal position and thereby support said cylinder in horizontal position in the space between the housing sections 110 and 112-. The rollers 128, one of which is a driving roller, are mounted on a Companion shaft 132 which is journaled for rotation in bearings carried by the standards 134. As clearly shown by FIGS. 2 and 3, shaft 132 is rotated by a sprocket chain 136 which engages the driving sprocket 138 and the driven sprocket 140, said driving sprocket 138 being actuated by the electric motor 142 through the reduction gearing indicated at 144.

As illustrated in FIG. 1, the successive samples which are to be investigated or analyzed in accordance with the present invention are supplied to the pump tube 12 from the supply device 146 which comprises a horizontal rotary member 148 which mounts a series of receptacles or cups, indicated at 150, for the different samples. Supply plate 148 is intermittently rotated and an off-take tube indicated at 152 is connected to the pump tube 12 and is pivotally movable in timed relation to the movement of plate 148 for moving its inlet end into and out of each of the receptacles 150 in succession during the dwell periods of said plate. This supply device 146 may be of the construction shown and described in U.S. Patent No. 2,879,141 or of the construction described in the application of Jack Isreeli, Serial No. 666,403, filed June 18, 1957.

The operation of the apparatus is believed to be clear from the above description. However, by way of a brief summary of the description of the operation of said apparatus, it will be noted that the samples of the liquid under investigation which may be a body liquid, such as blood serum, for clinical analysis, or any other substance for clinical analysis or for industrial investigation is supplied together with the acid and air or other inert gas through the pump tubes 12, 14 and 16, respectively. The air or other inert gas is introduced into the liquid stream for subdividing the latter into spaced segments of liquid separated by intervening segments of air for maintaining the tubular passages in clean condition to avoid contamination of one liquid sample by a preceding liquid sample. The segmented liquid stream is introduced at one end of the cylinder 24, in the peripheral groove 30 and as said cylinder rotates, the liquid fiows progressively in the helical groove 28 in contact with the highly heated surface of said cylinder longitudinally and peripherally thereof to the oflftake groove 32 at a point spaced longitudinally of the point at which the intake groove 30 is provided. In the course of its passage through cylinder 24, the liquid containing the sample to be investigated or analyzed is digested by the heated acid and is in highly concentrated condition by the time it reaches the outlet groove 32. This hot liquid is then cooled by passage through the cooling coil 38 and is diluted with water which is admitted through the pump tube 40. The liquid thus cooled and diluted is then conducted by tube 42 to the pump tube 44 and is mixed with water introduced by pump tube 46, for further dilution of the digested liquid, and from the mixing coil 50 where this further dilution takes place the liquid passes to the overflow supply receptacle 54. An aliquot of the diluted liquid is then transmitted by tube 62 and pump tube 66 to the fitting 72 where sodium hydroxide and air are introduced by the pump tubes 68 and 70, respectively, the air serving to segmentize the liquid stream as described above with reference to the air admitted through pump tube 16. From the mixing coil 74, the segmentized liquid stream passes to the inlet end of coil 78 where the alkaline phenol, one of the substances of the above-described color reagent is introduced. The other of the aboverdescribed color reagents, namely sodium hypochlorite, is transmitted by pump tube 82 between the mixing coils 78 and 84 and from the latter the liquid passes to the heating bath where the color is fully developed, after which the liquid passes through the cooling coil 88 and then through the flow cell of the colorimeter 99. As described above, acid fumes are removed by suction from the open inlet end of the cylinder 24 and are thus prevented from contaminating the air in the workroom or laboratory, said acid fumes being diluted with water and discharged to waste at the outlet 98 of the aspirator 96. Also, as described above,

the overflow tube 100 prevents spilling over of the liquid at the open outlet end of the cylinder in case of an excess of said liquid in the outlet groove 32.

The method and apparatus of the present invention, may be used for partial digestion of a substance under investigation when said substance is homogeneous, i.e., when it has only one source of nitrogen in its composition. In this connection, it will be understood that total digestion is employed, in accordance with known practice when the substance is not homogeneous, i.e., when it includes more than one source of nitrogen in its composition and the rates of digestion of said nitrogen sources are not relatively the same. Also, it will be understood that while the method and apparatus of the present invention are intended primarily for performing Kjeldahl type quantitative nitrogen determinations, the principles of this method and apparatus are not limited to such determinations, but may be used for other purposes.

As described above, the apparatus of the present invention is especially well adapted for continuous liquid analysis or liquid treatment involving digestion of proteins for total or partial nitrogen determinations. It will be understood, however, that the liquid-heater and other parts of the apparatus may be used for other purposes, for example, for heating boiler feed water together with an acid in a continuous analysis or monitoring method for total iron or copper determinations. The heating of the water increases the concentration of the iron or copper therein and thereby facilitates the analysis, the function of the acid, usually sulfuric acid, being to digest or render soluble in the water iron which may be present therein in a non-soluble form. Further, it will be understood that the liquid-heater may be used generally for the flash heating, of one or more liquids supplied thereto at one point in a flowing stream, for concentration or other purposes, concurrently with the withdrawal of the concentrated liquid from the heater at a point of delivery spaced downstream from said point of supply.

While I have shown and described the preferred embodiment of my invention, it will be understood that the invention may be embodied otherwise than as herein specifically illustrated or described, and that certain changes in the form and arrangement of parts and in the specific manner of practicing the invention may be made without departing from the underlying idea or principles of this invention within the scope of the appended claims.

What I claim is:

1, Continuous digestion and analysis apparatus, comprising a horizon-tally mounted longitudinally extending rotary member having a helical passage therein for the flow of a liquid from a point of liquid supply to a point spaced longitudinally and downstream of said point of supply when said member is rotated about its horizontal axis, means for rotating said member about said axis,

means for heating said member and thereby heating the liquid while it flows through said passage, stationary means in communication with said passage at said longitudinally spaced points thereof for the supply and delivery of liquid to and from said helical passage, respectively, during the rotation of said longitudinally extending memher about said axis, means including a proportioning pump for transmitting liquids in predetermined proportions to said heated rotary member through said stationary means at said supply point, means operable during prising a liquid-heating vessel mounted for rotation about a horizontal axis, means for rotating said vessel about said axis, means for heating said vessel during its rotation, liquid-inlet means in liquid-flow communication with said vessel for introducing a stream of liquid to said vessel during its rotation, said vessel having means for the flow of the liquid in contact with the inner heated surface thereof from said inlet means to a point downstream from said inlet means, liquid outlet means for the delivery of liquid from said vessel at said downstream point for the Withdrawal of liquid from said vessel during the rotation thereof and while the stream of liquid is being introduced into said vessel through said inlet means, means for treating the withdrawn liquid for colorimetric examination, a colorimeter having a flow cell, and means for transmitting a stream of said treated withdrawn liquid through said flow cell of the colorimeter for the colorimetric examination thereof.

3. Continuous digestion and analysis apparatus, comprising a liquid-heating vessel mounted for rotation about a horizontal axis, means forrotating said vessel about said axis, means for heating said vessel during its rotation, liquid-inlet means in liquid-flow communication with said vessel for introducing a stream of liquid to said vessel during its rotation, said vessel having helical passage means coaxial with the axis of rotation of said vessel for causing the liquid to flow in contact with the inner heated surface thereof from said inlet means to a point downstream from said inlet means, liquid outlet means for the delivery of liquid from said vessel at said downstream point for the withdrawal of liquid from said vessel during the rotation thereof and while the stream of liquid is being introduced into said vessel through said inlet means, means for treating the withdrawn liquid for colorimetric examination, a colorimeter having a flow cell, and means for transmitting a stream of said treated withdrawn liquid through said flow cell of the colorimeter for the colorimetric examination thereof.

4. Continuous digestion and analysis apparatus, comprising a liquid-heating vessel mounted for rotation about a horizontal axis, means for rotating said vessel about said axis, means for heating said vessel during its rotation, liquid-inlet means in liquid-flow communication with said vessel for introducing a stream of liquid to said vessel during its rotation, said vessel having means for the flow of the liquid in contact with the inner heated surface thereof from said inlet means to a point downstream from said inlet means, a liquid supply conduit in liquid-flow communication with said liquid-inlet means, proportioning pump means for introducing into said conduit a stream of a first liquid which is to be analyzed and a stream of a second liquid to act on said first liquid during said flow and the heating of the liquid in said vessel, liquid outlet means for the delivery of liquid from said vessel at said downstream point for the withdrawal of liquid from said vessel during the rotation thereof and while the stream of liquid is being introduced into said vessel through said inlet means, means for treating the withdrawn liquid for colorimetric examination, a colorimeter having a flow cell, and means for transmitting a stream of said treated withdrawn liquid through said fiow cell of the colorimeter for the colorimetric examination thereof.

5. Continuous digestion and analysis apparatus, com prising a liquid-heating vessel mounted for rotation about a horizontal axis, means for rotating said vessel about said axis, means for heating said vessel during its rotation, liquid-inlet means in liquid-flow communication with said vessel for introducing a stream of liquid to said vessel during its rotation, said vessel having helical passage means coaxial with the axis of rotation of said vessel for causingthe liquid to flow in contact with the inner heated surface thereof from said inlet means to a point downstream from said inlet means, a liquid supply conduit in proportioning pump means for introducing into said conduit a stream of a first liquid which is to be analyzed and a stream of a second liquid to act on said first liquid during said flow and the heating of the liquid in said vessel, liquid outlet means for the delivery of liquid from said vessel at said downstream point for the withdrawal of liquid from said vessel during the rotation thereof and while the stream of liquid is being introduced into said vessel through said inlet means, means for treating the withdrawn liquid for colorimetric examination, a colorimeter having a flow cell, and means for transmitting a stream of said treated withdrawn liquid through said flow cell of the colorimeter for the colorimetric examination thereof.

6. Continuous digestion and analysis apparatus, comprising a liquid-heating vessel mounted for rotation about a horizontal axis, means for rotating said vessel about said axis, means for heating said vessel during its rotation, liquid-inlet means in liquid-flow communication with said vessel for introducing a stream of liquid to said vessel during its rotation, said vessel comprising a cylinder having a helical groove therein coaxial with the axis of rotation of the vessel for causing the liquid to flow in contact with the inner heated surface thereof from said inlet means to a point downstream from said inlet means, a liquid supply conduit in liquid-flow communication with said liquid-inlet means, proportioning pump means for introducing into said conduit a stream of a first liquid which is to be analyzed and a stream of a second liquid to act on said first liquid during said flow and the heating of the liquid in said vessel, liquid outlet means for the delivery of liquid from said vessel at said downstream point for the withdrawal of liquid from said vessel during the rotation thereof and while the stream of liquid is being introduced into said vessel through said inlet means, means for treating the withdrawn liquid for colorimetric examination, a colorimeter having a flow cell, and means for transmitting a stream of said treated withdrawn liquid through said flow cell of the colorimeter for the colorimetric examination thereof.

7. Continuous digestion and analysis apparatus, comprising a liquid-heating vessel mounted for rotation about a horizontal axis, means for rotating said vessel about said axis, means for heating said vessel during its rotation, liquid-inlet means in liquid-flow communication with said vessel for introducing a stream of liquid to said vessel during its rotation, said vessel having means for the flow of the liquid in contact with the inner heated surface thereof from said inlet means to a point downstream from said inlet means, liquid outlet means for the delivery of liquid from said vessel at said downstream point for the withdrawal of liquid from said vessel during the rotation thereof and while the stream of liquid is being introduced into said vessel through said inlet means, liquid-removal means additional to said outlet means for limiting the level of liquid in said vessel, means for treating the withdrawn liquid for colorimetric examination, a colorimeter having a flow cell, and means for transmitting a stream of said treated withdrawn liquid through said flow cell of the colorimeter for the colorimetric examination thereof.

8. Continuous digestion and analysis apparatus, comprising a liquid-heating vessel mounted for rotation about a horizontal axis, means for rotating said vessel about said axis, means for heating said vessel during its rotation, liquid-inlet means in liquid-flow communication with said vessel for introducing a stream of liquid to said vessel during its rotation, said vessel having means for the flow of the liquid in contact with the inner heated surface thereof from said inlet means to a point downstream from said inlet means, liquid outlet means for the delivery of liquid from said vessel at said downstream point for the Withdrawal of liquid from said vessel during the rotation thereof and while the stream of liquid is being introduced into said vessel through said inlet means, suction-operated stationary means in communication with the interior of said vessel for removing non-liquid fiuids from said vessel during said rotation of the vessel, means for treating the withdrawn liquid for colorimetric examination, a colorimeter having a flow cell, and means for transmitting a stream of said treated withdrawn liquid through said flow cell of the colorimeter for the colorimetric examination thereof.

9. Continuous digestion and analysis apparatus, comprising a liquid-heating vessel mounted for rotation about a horizontal axis, means for rotating said vessel about said axis, means for heating said vessel during its rotation, liquid-inlet means in liquid-flow communication with said vessel for introducing a stream of liquid to said vessel during its rotation, said vessel having means for the flow of the liquid in contact with the inner heated surface thereof from said inlet means to a point downstream from said inlet means, liquid outlet means for the delivery of liquid from said vessel at said downstream point for the withdrawal of liquid from said vessel during the rotation thereof and while the stream of liquid is being introduced into said vessel through said inlet means, means for adding a liquid to the withdrawn liquid to dilute it, a receptacle to receive the diluted withdrawn liquid, proportioning pump means for transmitting in predetermined proportions an aliquot of liquid from said receptacle and a liquid for treating said aliquot of liquid for colorimetric examination, and colorimeter means operable concurrently with the transmission and said treatment of said aliquot of liquid for the quantitative analysis of said aliquot in respect to a known ingredient thereof.

10. Continuous digestion and analysis apparatus, comprising a liquid-heating vessel mounted for rotation about a horizontal axis, means for rotating said vessel about said axis, means for heating said vessel during its rotation, liquid-inlet means in liquid-flow communication with said vessel for introducing a stream of liquid to said vessel during its rotation, said vessel having means for the flow of the liquid in contact with the inner heated surface thereof from said inlet means to a point downstream from said inlet means, liquid outlet means for the delivery of liquid from said vessel at said downstream point for the withdrawal of liquid from said vessel during the rotation thereof and while the stream of liquid is being introduced into said vessel through said inlet means, liquid-removal means additional to said outlet means for limiting the level of liquid in said vessel, means for adding a liquid to the withdrawn liquid to dilute it, a receptacle to receive the diluted withdrawn liquid, proportioning pump means for transmitting in predetermined proportions an aliquot of liquid from said receptacle and a liquid for treating said aliquot of liquid for colorimetric examination, and colorimeter means operable concurrently with the transmission and said treatment of said aliquot of liquid for the quantitative analysis of said aliquot in respect to a known ingredient thereof.

11. Continuous digestion and analysis apparatus, comprising a liquid-heating vessel mounted for rotation about a horizontal axis, means for rotating said vessel about said axis, means for heating said vessel during its rotation, liquid-inlet means in liquid-flow communication with said vessel for introducing a stream of liquid to said vessel during its rotation, said vessel having helical passage means coaxial with the axis of rotation of said vessel for causing the liquid to flow in contact with the inner heated surface thereof from said inlet means to a point downstream from said inlet means, liquid outlet means for the delivery of liquid from said vessel at said downstream point for the withdrawal of liquid from said vessel during the rotation thereof and while the stream of liquid is being introduced into said vessel through said inlet means, means for adding a liquid to the withdrawn liquid to dilute it, a receptacle to receive the diluted withdrawn liquid, proportioning pump means for transmitting in predetermined proportions an aliquot of liquid from said receptacle and a liquid for treating said aliquot of liquid for colorimetric examination, and colorimeter means operable concurrently with the transmission and said treatment of said aliquot of liquid for the quantitative analysis of said aliquot in respect to a known ingredient thereof.

12. Continuous digestion and analysis apparatus, comprising a liquid-heating vessel mounted for rotation about a horizontal axis, means for rotating said vessel about said axis, means for heating said vessel during its rotation, liquid-inlet means in liquid-flow communication with said vessel for introducing a stream of liquid to said vessel during its rotation, said vessel having helical passage means coaxial with the axis of rotation of said vessel for causing the liquid to flow in contact with the inner heated surface thereof from said inlet means to a point downstream from said inlet means, liquid outlet means for the delivery of liquid from said vessel at said downstream point for the withdrawal of liquid from said vessel during the rotation thereof and while the stream of liquid is being introduced into said vessel through said inlet means, liquid-removal means additional to said outlet means for limiting the level of liquid in said vessel, means for adding a liquid to the withdrawn liquid to dilute it, a receptacle to receive the diluted withdrawn liquid, proportioning pump means for transmitting in predetermined proportions an aliquot of liquid from said receptacle and a liquid for treating said aliquot of liquid for colorimetric examination, and colorimeter means operable concurrently with the transmission and said treatment of said aliquot of liquid for the quantitative analysis of said aliquot in respect to a known ingredient thereof.

13. Continuous digestion apparatus, comprising a liquid-heating vessel mounted for rotation about a horizontal axis, means for rotating said vessel about said axis, means for heating said vessel during its rotation, liquid-inlet means in liquid-flow communication with said vessel for introducing a stream of liquid to said vessel during its rotation, said vessel comprising a cylinder having a helical groove therein coaxial with the axis of rotation of the evssel for causing the liquid to flow in contact with the inner heated surface thereof from said inlet means to a point downstream from said inlet means, liquid outlet means for the delivery of liquid from said vessel at said downstream point for the withdrawal of liquid from said vessel during the rotation thereof and while the stream of liquid is being introduced into said vessel through said inlet means, and liquidremoval means additional to said outlet means for limiting the level of liquid in said vessel.

14. Continuous digestion apparatus, comprising a liquidheating vessel mounted for rotation about a horizontal axis, means for rotating said vessel about said axis, means for heating said vessel during its rotation, liquid-inlet means in liquid-flow communication with said vessel for introducing a stream of liquid to said vessel during its rotation, said vessel comprising a cylinder having a helical groove therein coaxial with the axis of rotation of the vessel for causing the liquid to flow in contact with the inner heated surface thereof from said inlet means to a point downstream from said inlet means, liquid outlet means for the delivery of liquid from said vessel at said downstream point for the withdrawal of liquid from said vessel during the rotation thereof and while the stream of liquid is being introduced into said vessel through said inlet means, liquid-removal means additional to said outlet means for limiting the level of liquid in said vessel, and suction-operated stationary means in communication with the interior of said vessel for removing non-liquid fluids from said vessel during said rotation of the vessel.

15. A continuous digestion and analysis method according to which there is employed a horizontal rotary member provided with a liquid passage extending helically around the axis of rotation of said member, said method comprising rotating said member about said axis and heating said member while it rotates, introducing into said liquid passage at a predetermined point a stream of liquid containing the substance to be digested and an acid for digesting said substance, withdrawing from said rotary member during the rotation thereof and at a point downstream in relation to said first mentioned point a stream of the liquid containing the digested substance, regulating the quantity of said liquids which flow into and out of said cylinder so that the liquid flows in said helical passage only during the rotation of said rotary member so that mixing of successive portions of the liquid stream during the flow through said passage is prevented, and subjecting the withdrawn stream of liquid during the flow thereof to treatment for quantitative analysis in respect to said digested substance.

16. A continuous method of digestion and analysis of a substance for nitrogen determination, according to which there is employed a horizontal rotary member having a helical groove providing a liquid passage extending helically' around the axis of rotation of said member, said method comprising rotating said member about said axis and heating said member while it rotates, introducing into said liquid passage a stream of liquid containing the sub stance to be digested and an acid for digesting said substance, regulating the quantity of said liquids which flow into and out of said cylinder so that the liquid flows in said helical passage only during the rotation of said rotary member so that mixing of successive portions of the liquid stream during the flow through said passage is prevented, withdrawing from said rotary member during the rotation thereof and at a point downstream in relation to said first mentioned point a stream of the liquid containing the digested substance, and subjecting the withdrawn stream of liquid during the flow thereof to treatment for quantitative analysis in respect to the nitrogen content thereof.

17. A continuous method of digestion and analysis of a substance for nitrogen determination, according to which there is employed a horizontal rotary member provided with a liquid passage extending helically around the axis of rotation of said member, said method comprising rotating said member about said axis and heating said member while it rotates, introducing into said liquid passage a stream of liquid containing the substance to be digested and an acid for digesting said substance, regulating the quantity of said liquids which flow into and out of said cylinder so that the liquid flows in said helical passage only during the rotation of said rotary member so that mixing of successive portions of the liquid stream during the flow through said passage is prevented, withdrawing from said rotary member during the rotation thereof and at a point downstream in relation to said first mentioned point a stream of the liquid containing the digested substance, and subjecting the withdrawn stream of liquid during the flow thereof to treatment for quantitative analysis in respect to the nitrogen content thereof, said further treatment comprising the addition of water as a diluent liquid and an alkali to neutralize the acid in said withdrawn stream of liquid and to release ammonia therefrom with concomitant formation of ammonium hydroxide, in said last mentioned stream, as a result of the solution of the released ammonia in the liquid diluent, and the addition of a color reagent to the stream containing the ammonium hydroxide for colorimetric analysis of said last mentioned stream in respect to ammonia as a measure of the nitrogen content of said digested substance.

18. A continuous method of digestion and treatment for analysis of a substance for nitrogen determination, comprising transmitting a stream of liquid containing an acid and the substance to be digested by said acid through a heated vessel at a regulated flow rate therethrough and thereby effecting the digestion of said substance during the flow of the liquid through said vessel, concomitantly withdrawing from said vessel liquid containing the substance in digested condition, diluting the liquid withdrawn from said vessel without interrupting the flow thereof, thereafter adding sodium hydroxide to the diluted stream, and thereafter treating the stream of liquid for colorimetric examination.

19. A continuous method of analysis of a substance for nitrogen determination, comprising transmitting a stream of liquid containing an acid and the substance to be digested by said acid through a vessel having a helical passage in a heating Zone and thereby efiecting the digestion of said substance during the flow of the liquid through said zone, concomitantly withdrawing from said vessel liquid containing the substance in digested condition, diluting the liquid withdrawn from said vessel with- 12 out interrupting the fiow thereof, and continuing without interruption the flow of the liquid stream, adding sodium hydroxide to the diluted stream during the flow thereof, thereafter treating the flowing stream of liquid for colorimetric examination, and colorimetrically examining the last mentioned stream of liquid while it continues to flow.

References Cited in the file of this patent UNITED STATES PATENTS 2,137,051 Jain Nov. 15, 1938 2,173,546 Bowers Sept. 19, 1939 2,686,754 Monod Aug. 17, 1954 2,797,149 Skeggs June 25, 1957 2,880,070 Gilbert Mar. 31, 1959 2,899,280 Whitehead Aug. 11, 1959 

17. A CONTINUOUS METHOD OF DIGESTION AND ANALYSIS OF A SUBSTANCE FOR NITROGEN DETERMINATION, ACCORDING TO WHICH THERE IS EMPLOYED A HORIZONTAL ROTARY MEMBER PROVIDED WITH A LIQUID PASSAGE EXTENDING HELICALLY AROUND THE AXIS OF ROTATION OF SAID MEMBER, SAID METHOD COMPRISING ROTATING SAID MEMBER ABOUT SAID AXIS AND HEATING SAID MEMBER WHILE IT ROTATES, INTRODUCING INTO SAID LIQUID PASSAGE A STREAM OF LIQUID CONTAINING THE SUBSTANCE TO BE DIGESTED AND AN ACID FOR DIGESTING SAID SUBSTANCE, REGULATING THE QUANTITY OF SAID LIQUIDS WHICH FLOW INTO AND OUT OF SAID CYLINDER SO THAT THE LIQUID FLOWS IN SAID HELICAL PASSAGE ONLY DURING THE ROTATION OF SAID ROTARY MEMBER SO THAT MIXING OF SUCCESSIVE PORTIONS OF THE LIQUID STREAM DURING 